1. Field of the Invention
The present invention relates to a gas burner for a gas dryer which produces an even and well dispersed flame distribution, with low consumption of fuel and reduced noxious emissions such as carbon monoxide. In another aspect, the present invention relates to a heater assembly for a gas clothes dryer which employs such a burner.
2. Discussion of the Prior Art
Gas burners are used in a number of applications ranging from furnaces, gas clothes dryers and other like applications in which it is desired to heat air for use for various purposes. A universal requirement for all burners is that they should be efficient in burning fuel supplied, generally are required to provide a desired flame profile depending on the application, should be quiet and should not produce large amounts of potentially harmful bi-products such as carbon monoxide.
In the case of the use of such burners in household applications, one current prominent use is in clothes dryers, typically clothes dryers using natural gas as a fuel. Such dryers can be a popular amenity for households of all incomes since consumers can dry two loads of clothes in a natural gas dryer, on average, for the amount of money it costs to dry just one load in an electric dryer.
For additional savings and energy conservation, current natural gas dryers use electronic ignition systems instead of a continuously burning pilot light. Generally such dryers work by moving warm air through the clothes inside. Inside of the dryer is a rotating drum and the dry heated air created by a natural gas burner flows over and through the clothes as the drum tosses them through the air. The moist air coming off the clothes is exhausted through a vent to the outdoors, and is replaced by more dry heated air.
Due to current energy costs, it is very important that burners employed in heaters in natural gas dryers function with high efficiency while providing a wide flame distribution to heat a maximum amount of air. This provides a large flow of warm air to clothes being dried. It is also important that such burners avoid producing harmful or noxious byproducts such as carbon monoxide, due to the fact that even though gas dryers are vented generally to the outside, they are still used in enclosed home, and typically within smaller rooms such as laundry rooms. If such bi-products are produced at any high level, there is a high risk of harm to occupants or pets of the homes, and in particular, to operators of the gas clothes dryer.
In the past design of burners, it has been recognized that unintended secondary airflow around the burner head or nozzle of a burner can result in imperfect burning of fuel with resultant undesirable by-products. One prior art burner recognizes that the burning of fuels can result in the formation of nitrogen oxides (NO2), which when released to the atmosphere constitute pollutants.
In order to avoid such bi-products, one approach involves providing a fuel discharge nozzle with a shielding cone, which is generally disk shaped and includes a plurality of openings formed therein for allowing passage of a limited amount of air therethrough. The cone is an attempt to create a protected area adjacent the nozzle. However, as a result of the air flowing through openings in the cone, there still results an incomplete burning of fuels with resultant undesirable bi-products. Moreover, there is also caused a redirection of the flame in the direction of the secondary air being passed through the openings in the cone.
Another attempt to influence fuel burning with a burner involves an arrangement, which produces flames as long, slender rod like jets of great length. In this burner arrangement, one or more principal orifices are placed symmetrically on or about the axis of a pipe. The principal flow of gas is through these principal orifices. Secondary jets issue from the pipe at an angle to the axis of the pipe. The secondary orifices are shielded by a baffle surrounding the orifices which also includes openings for inducing air into the space adjacent to the secondary orifices, thereby also affecting the direction of the flame and the burning efficiency.
In yet still another arrangement, a conical shroud is provided shaped to avoid lateral divergence of flames. Such an arrangement results in an essentially unidirectional flame, which is not well suited for heating large volumes of air.
In accordance with the present invention, the problems of the prior art are avoided by providing a burner for use, in particular, with a gas clothes dryer, which functions efficiently in terms of consumption of fuel, produces a substantially constant flame with low levels of undesirable bi-product emissions, is not subject to adverse effects on the flame resulting from secondary air flow, and provides a flame which is dispersed over a wide area to provide heating of large volumes of air for use in a dryer.